DISTRIBUTION OF S-HAPLOTYPES AND ITS RELATIONSHIP WITH SELF-INCOMPATIBILITY IN BRASSICA-OLERACEA .1. IN INBRED LINES OF CAULIFLOWER (BRASSICA-OLERACEA VAR BOTRYTIS)

Self-incompatibility in the Brassicaceae is controlled by the single m ultiallelic S-locus which contains at least two genes expressed in the stigma, the SLG (S-locus glycoprotein) and SRK (S-locus receptor kina se)genes. The presence of two transcriptional units at the S-locus led to the use of the term S-haplotype to define allelic forms of the S-l ocus. On the basis of sequence data obtained for SLG and SRK from diff erent S-haplotypes, two classes of S-haplotypes have been described in Brassica. Here, we report the identification of S-haplotypes in 126 p lants representing 82 open-pollinated cultivars of B. oleracea var 'bo trytis' (cauliflower) by means of an immunochemical analysis of SLG pr oducts. The antibodies used enabled class I and class II S-haplotypes to be discriminated. Ten different S-haplotypes were identified, eight of class I, only one belonging to class II and another one for which no SLG products were detected by our antibodies. In heterozygous plant s containing the class II S-haplotype associated with some particular class I S-haplotypes, specific modifications of class II SLGs were fou nd. Pollen tube counts and seed set were used and compared to assess t he self-incompatibility phenotypes. SC, a class I haplotype, was alway s found to be associated with a fully self-compatible phenotype. Half of the plants analyzed possessed the class II S-haplotype. Plants homo zygous for this haplotype showed various levels of self-incompatibilit y, from highly selfincompatible to fully self-compatible. These result s are discussed with specific reference to, F-1 hybrid breeding.